Specific interactions between biological macromolecules such as proteins, oligonucleotides, and oligosaccharides provide the chemical foundation for all cellular processes. Characterizing these interactions is essential to defining the biological function of a macromolecule at the molecular level. The role of the Protein Interaction Shared Resource is to provide Cancer Center researchers with easy access to the advanced technologies used in characterizing binding interactions. Currently, a BIACORE 2000 optical biosensor is used to define the assembly state, affinity, a kinetics of an interaction. In a typical biosensor experiment one of the interacting molecules is immobilized onto a surface and the second is passed over this surface in solution. When the molecules interact to form a complex, a response is registered using the optical phenomena of surface plasmon resonance. Since binding reactions are monitored in real time, it is possible to interpret kinetic information about the interaction. Given the complexities involved in biosensor analysis, investigators work closely with the facility's director, Dr. David Myszka, to ensure that experiments are designed properly and that the data are interpreted correctly.